Safety device for pyrometers



April 8 1924.

R P. BROWN SAFETY DEVICE FOR PYROMETERS Filed Feb. 20.

1922 2 Sheets-Sheet 1 0 a 5/ 5 CW fiw 1 0 f U: Q 3 I 1 5 I. w 3.1 f 4 o A ATTORNEY Patented Apr. 8, 12 24.

UNITED STATES 1,489,920 PATENT OFFICE.

RICHARD P. EEowN, OF PHILADELPHIA, PENNSYLVANIA, AssIoNoE TO THE BEowN INSTRUMENT COMPANY, P PHILADELPHIA, PENNSYLVANIA, A coEPoEA'noN 0E PEN NSYLVANIA.

SAFETY DEVICE FOR PYRDMETERS.

Application filed. February a0, 1922. Serial No. 538,114.

Devices for Pyrometers, of which the following is a specification.

Some of the objects of the present inven tion are to provide a safety control means for pyrometers, thermo-couples, furnace control devices, gas, liquid and vapor actuated instruments, or any other instrument wherein operation beyond a predetermined limit may result in a condition of danger; to provide an alarm system for indicating recording, and any other instruments; to provide means to prevent a heating unit from overheating in case the controlling device ceasesto 'fun'c tion; to provide an emergency control for heating units arranged to operate automativ Iform'is located at a furnace '22 or in' anycally if the thermo-couple circuit of the heating unit becomes inoperative, to providemeans for automatically cutting out'o r shutting down a heating unit under excess temperature conditions; to provide means for rendering a safety device for a heating unit inefi'ective under certain conditions;jand to provide other improvements as will hereinafter appear. H

In the accompanying drawings, Fig. 'l'represents a detail, in plan, of a measuringin- I vstrument equipped with one form of the present invention; Fig. 2 represents a front elevation of the same Fig. 3 represents a diagram of a pyrometric system embodyingjth present invention; and Fig. 4: represents a diagram of another formof the invention.

Referring to the drawings, one form of the present invention is shown as applied to a pyrometric system including an electrical measuring instrument 10, here shown as of.

-scribed in 'a co-pending application Serial 1N0. 492,937, and may be here briefly described as a contact" control comprising'a contact member 11 arranged to be adj ustably carried .by a cross-piece 12 which is fixed to a movable pivoted bar 13, generally known as the de I vpression bar. The bar 13 in the present construction, is provided with a slot 14, through or zone temperature.

thereof, both of said contactors 16 and 17 being positioned to engage a common contact 18. The 'contactors 16 and 17 are arranged to be selectively actuated by the index or pointer 20 of the instrument 10 as the depressor bar 13 functions. It will be under-.

stood that the contact member 11 is'fixed in,

a position on the instrument 10 corresponding to the predetermined constant temperature desired to be maintained, the contactor 16 be'- ing on the low side and thecontactor 17', be'=. "ing on the high side of the desired tempera-i. .ture.-

A thermo-couple v21 of any well known otherheat'zone to be controlled and has leads 23" and 24 connected to the instrument 10 to actuate these'nsitiveelement thereof in the usual manner tocause the pointer 20 to move to a position corresponding to the furnace For controlllng the temperature .of the furnace 22.an. electric heating unit 25 is provided one terminal of which is connected by a conductor 26 to onesideof the service line or source of current 'whilethe other terminal thereof is connected by alconductor 27 to a movable circuit closer arm ,28 of an auto matic control switch 30. The arm 28 is pivotally mounted to move to open position by gravity and to be closed by the magnetic action of arelay coil 31, bringing-it into @11 gagement with the contact 32 which is con-'"' nec'ted to the opposite side of the service line.

The relay coil 31 is arranged'to beene-rgized and deener' 'zed by two circuits including respective y the contactors 16 and 17 and having a common return through the The low temperature circuit,

contact 18. I which is the-one to energize the coil 31 to cause the unit 25 to heat the furnace, comrises the contactor 16, apconductor 33 lead- 36 to binding post 0 and a conductor 37 toj' common contact 18.

The high temperature circuit comprises the contactor 17, a conductor 38, to binding post H, conductor 40 to one side of service line, across the line to conductor 41, a resistance 42 and the conductor 36 to binding post C to the common contact 18. The contact 32 is connected to the conductor 35, so that,

when the arm 28 contacts therewith, current will flow to the heating unit 25.

As fully explained in the above mentioned copending application, the circuits including the contactors 16 and 17 may be arranged to also operate signal lights or other alarm devices to give notice of danger or limit temperature.

It will be apparent from the foregoing that the functioning of the instrument pointer 20, by which the control circuits are selected, is dependent upon the proper functioning of the thermo-couple 21 and its circuit, so that should it cease to operate there would be no further control of the heat unit 25. Thus, if the circuit of the thermo-couple 21 should break, or the thermo-couple 21 become inoperative while the heating unit 25 was heating, the pointer 20 would at once return to its zero position, and in consequence when the temperature reached the predetermined limit there would be nothing to out off the heating unit 25 and the temperature would continue to rise.

For the purpose of automatically cutting out or shutting down the heating unit in the event above referred to, namely the failure of the thermo-couple circuit to function, an auxiliary or safety circuit is provided including a conductor 43, contactor 44, con-.

tact 45 and conductor 46, the two conductors 43 and 46 being respectively connected to the binding posts G and H, so that this auxiliary circuit is connected in multiple with the high temperature circuit, which when closed deenergizes the relay coil 31. The contactor 44 and contacts 45 are suitably mounted Within the casing of the instrument 10 in a position to locate the contactor 44 in the path of movement of the pointer 20, when the latter is in its zero position, so that the action of the depressor bar 13 is to cause the pointer 20 to shift the contactor 44 into engagement with the contact 45 to thereby close the control circuit which deenergizes the coil 31. This circuit is from contact 45, conductor 46, binding post I-I, conductor 40, across service line to conductor 41, resistance 42, conductor 36 to binding post C,conductor 43' to contactor 44. The closing of this circuit short circuits the coil 31 so that the switch arm 28 returns by gravity to its open circuit position and thus breaks the heating unit circuit so that there is no furthen increase in temperature. Of course, when the depressor bar 13 rises the contactor44breaks contact with contact 45 and the short circuit around the coil 31 is broken and the current again flows from the service line through the coil 31, but the magnetic pull under this condition is not suiricient to actuate the switch arm 28 because of the re sistance 42.now in series with the coil 31.

In the foregoing emergency or safety system it will be noted that the pointer 20 is in its zero or initial position when the safety contacts are caused to function, and since the pointer 20 is also in this zero position at starting time under normal conditions, it is desirable to provide a means to prevent the emergency circuit from functioning, as otherwise there would be no heating of the furnace at all. To that end one means for accomplishing this result consists of a spring arm 47 fixed at one end to the casing of the instrument 10 and having a free end in close proximity to the normal zero position of the pointer 20, and arranged to engage the said pointer 20. A feed screw, 48 is threaded through the casing 10 into position to engage the arm 47 so that when fed inwardly it will move the arm 47 to shift the pointer 20 manually out of alinement with the contactor 44. When this is accomplished the system may be started and as the pointer 20 cannot engage the contactor 44, the heating unit functions under the control of the instrument as long as the thermo-couple circuit is operative. As soon as the system has operated sufliciently to retain the pointer 20 beyond the contactor 44, the screw 48 is backed off to its normal position, and thereby releases the spring arm 47 which then returns to a position where it will not interfere with the pointer 20 should the latter return to its normal zero point. Now, if the thermo-couple 21 ceases to function or there is a break in its circuit, the pointer 20 immediately swings back to the initial position above the contactor 44 and consequently the next operation of the depressor bar 13 moves the pointer 20 to close the safety circuit through the contactor 44 and contact 45. As a result the line current short circuits the coil 31 by traversing conductor 36 to binding post C, and thence by contactor 44 and contact 45 to the line. This releases the switch arm 28 so that the circuit of the heating unit is broken and no further rise in temperature can take place.

In order that notice may be given that the heating unit has shut down, and thus prevent the furnace from cooling down too much, it is preferable to connect an alarm signal 49 into the emergency circuit, for example, connecting a bell or a lamp with the conductor 46 so that an attendant may be promptly advised of the changed condition of the system.

In the form of the invention shown in Fig. 4, a suitable electrically operated switch 50 is arranged to control the opening and closing of a circuit 51 which is arranged .to operate an, electric furnace, a valve,

a servlice'hne, so that the arm GObecOmes'a 'or' any The operative. and ino I the switch 50 are norma 1 controlled IQSPQC";

other electrically controlled device, rative positions of tively by. acircui-t Linc uding a contact 52 bio and}; contact'or 53 and a circuit- H including service'line'to the switc" 50.

measuring instrument is broken, a rocker arm-60 is provided and jpivotediat .61 just below the zero-position of the pointer 20.

' This arm (SO-carries two contactors 62 and63 arranged at, opposite sides. of the pivot. 61, which 62 is locatedto be actuated by the ointer 20 when it is in the zero position,

'whi'e-the other} 63 is somewhat removed --there-from "on the high side of the 'instrur ment scale. Trip members'64 and -(iii-projectfrom the respectiveends' ofthearm '60 so thatone orthe other is in the path of' movement of the pointer 20 according to the tilted p'osition of the arm 60. A spring 66 Oneo'f'these circuits includes ,a contact 70,;

may be provided, if desired, to accelerate the tilting movementof the arm when struck by the pointe'r 2.0. The arm 60 is connected by a conductor 67 to Ioneside ofthe selecting .means for two -control circuits.-

arrangedzto be engaged by the contaetor.;62,

a con uctor 71,'a sprlng arm 73 and either a connection 74 with the circuit L or a connection-"75 with the circuit H. The other. :.of. thesecircuits includes a contact 76, ar-= ranged "m be engaged'fby the icontactor"63, a solenoid coil 77 and a conductor 78 to the other side of the service" line. Theselection' ,y h p i arm 73 is determined by a rejection 80 from the c0re.81 of the -solenoid .77 and two contactors 8 2 and 83 fixed to the springarm ,limitedfio any specifi .of the circu'itL or circuit H' 73 and arranged respectivelyeto engage contacts 84 and 85, the former ing in the cir- 'cuit -L andthe latter in the I circuit When the solenoid 77 is 'deenergized the rojection 80 rests u n the arm 73'to break t e contact ii: contactor 83- and the contact 85 while makin the contact'betweenthe con between-t tactor 82 an the contact 84; This is the condition of the stem'at'starting times so .is closed to cause the s a'ry to maintain the sa ety portion o'f the circuit'L open and for this purpose a second so1enoid'86 is provided having a keeper from the latch to been 'ag tact betweenflthe contactor 62 and Having thus descri claim: 1. In an electrical systemya heating unit;

'energized, itlwill be engaged by the keeper 79.

87 Thesolenoid8'6 is connected directly to the-service line-so -that itis'energized at all times when the main current is on.

- The operation of 'this ffor'm' of the' inven tion is as follows: In;-Fig. 4 the'liarts are in ;75--

starting position and consequent y the con.- trol sw'1tch50 .is energized' by the circuit as soonias the current sturned on, As soon as the measuring instrument responds pointer 20 moves to the right as. 80 seen in Fi 4, and thereby, either under the action of t e-depressor-bar 13-or by striking current the the trip member- 365, causes the arm 60- to tilt thereb breaking contact between contactor 62 a'n thecontact 70,.and' making contact 85 between'the. contactor 63.an d the contact '7 6.

Thiscloses the circuit through the solenoid 7 and causes the core 8 1'to-'1ift out of en- 'gagementwith the .-s 'ringe arm/Z3 and its by the keeper .87 and 1 Q held elevated while the thus thereafter, system is in operation. The 's ring arm 73, being free,-breaks the circuit 0 contactor 82 and" contact 8t'but brings the contactor 83 into engagement with the contact 85." This leaves the safety circuit 'H open only between-the contactor 62 and the contact 70.-

The"syste ml'can now. operate continuously in therequiredmanner. *If,' however, the

-' instrument. circuit "should; become broke-n through accident or otherwise, the pointer 20 immediately brings back-tozero position, thereby.striking therocker arm'60 and causing it "to-shift to break 1 the 'circuit' of con- "tactor 63 and the contact 76 but. closing'conp the contact .70 which closes the safety circuitH. to

cause the control switch 50 to break the 0p eratingicircuit- 51-andthus shut down the heating unit orother controlled device. -to prevent overheating orvoper'ation beyond the; intended limit. a 9

Although only. :two', are shown in which. nus invention mav. be embodied,;it*-' a .isto 'be-understoodthatthe inventionisnot 0' construction, but

might be a plied l'n. various forms without depa'rtin'g' mm the spirit of the invention or the s'copeof-the specified claimaa pyrometer arranged to control-said heat: in'g unit, and means rendered a erative by an inoperative conditionofsai "pyrom'eter T2 for-scausing' said heating.,-unit shutdOWIlcontrolled by saidheating and control- 1130 my invention,- T

ling said instrument, and means for automatically shutting down said heating unit in case said thermo-couple ceases to control said instrument.

3. In an electrical system, a heating unit, a measuring instrument provided with a pointer, means controlled by the temperature of said heating unit for operating said measuring instrument, and emergency means located adjacent the normal zero of said instrument and controlled by said pointer for shutting down said heating unit under abnormal conditions.

4. In an electrical system, a heating unit, a measuring instrument provided with a pointer, means controlled by the temperature of said heating unit for operating said measuring instrument, emergency means located adjacent the normal zero of said instrument and controlled by said pointer for shutting down said heating unit under abnormal conditions, and means for rendering said emergency means inoperative under starting conditions.

5. In an electrical system, a heating unit, a measuring instrument provided with a pointer, means controlled by the temperature of said heating unit for operating said measuring instrument, emergency means located adjacent the normal zero of said instrument and controlled by said pointer for shutting down said heating unit under abnormal conditions, and means including a pointer shifting device for rendering said emergency means inoperative under starting conditions.

6. In an electrical system, the combination of an electrical instrument, an actuating circuit for said instrument, a device to be operated, a circuit for controlling said device, and means actuated by the failure of said actuating circuit to function and operating through said control circuit to render said device inoperative.

7. In an electrical system, the combination of an electrical instrument, an actuating cir cuit for said instrument, a device to be operated, a circuit controlled by said instrument for controlling said device, and means actuated by the failure of said actuating circuit to function and operating through said control circuit to render said device inoperative.

8. In an electrical system, a device to be operated; a circuit for controlling said device, a measuring instrument provided with a pointer and arran ed to control said circuit, an actuating circuit for said instrument, and means controlled by said pointer when said actuating circuit isbroken and operating through said control circuit for rendering-said device inoperative.

9. In an electrical system, a device to be operated, a circuit for controlling said device, a measuring instrument provided with a pointer and arranged to control said circuit, an actuating circuit for said instrument, and safety means including \a switch operated by said pointer when returned to zero position by a break in said actuating circuit for rendering said device inoperative.

l0. In-an electrical system, a device to be operated, a circuit for controlling said device, a measuring instrument provided with a pointer and arranged to control said circuit, an actuating circuit for said instrument, safety means including a switch operated by said pointer when returned to zero position by a break. in said actuating circuit for rendering said device inoperative, and means for rendering said safety means ineffective under starting conditions;

11. IIkflIl electrical system, a device to be operated, a circuit for controlling said device, a measuring instrument provided with a pointer and arranged to control said circuit, an actuating circuit for said instrument, safety means including a switch operated .by said ointer when returned to zero position by a break in said actuating circuit for rendering said device inoperative, and means including a solenoid controlled switch for connecting said safety means to said control circuit.

Signed at Philadelphia, in the county of Philadelphia and State of Pennsylvania, this 7 day of February, 1922.

RICHARD P. BROWN. 

